Very little is known about Ewloe Castle, other than it appears to have been built by Llywelyn ap Gruffydd to counter the English fortresses in eastern Gwynedd of Hawarden and Flint.  It was built in a hollow beneath a field, that actually set on a small hill overlooking two creeks:  the Wepre and the New Inn Brook.

“Ewloe castle rises at northwest of the town of Hawarden and is one of the symbols of the brief triumph of the Welsh prince Llywelyn the Last that began its construction in 1257 after the reconquest of this part of Wales. Of all the native castles in North Wales Ewloe is the only with a non spectacular setting. It stands on a promontory overlooking the junction of two streams but is overwhelmed by higher ground at south. Its position, near the English border, was very strategic at control of the road to Chester. It stood within the forest of Ewloe, surrounded by woods and in a great position for hunting.”
http://www.greatcastlesofwales.co.uk/ewloe.htm

“Essentially, the plan of Ewloe Castle is semi-circular, formed with two separate sections, the Upper Ward with the great Welsh Tower and the Lower Ward where the daily activity was centered. Around the perimeter are two critical defensive features: the lengthy rock-cut ditch and steeply sloping embankments, and the extensive curtain wall which encompasses both wards.

From above, the most noticeable structure is the great Welsh Tower. For several years controversy has cloaked this tower. Citing its similarities to other Welsh towers, such as at Castell- y-Bere where there is concrete evidence that Llywelyn the Great built the stronghold, many scholars have theorized that the Welsh Tower was also built in the early 1200’s by the great Llywelyn ab Iorwerth. However, CADW: Welsh Historic Monuments now supports the theory that the latter Llywelyn ap Gruffydd was the founder of the great tower. They base their decision on evidence from documents dating to 1311 which state that Llywelyn ap Gruffydd erected a “castle in the corner of the wood” in 1257 (Renn and Avent, 1995).”  http://www.castlewales.com/ewloe2.html

Also on the Castles of Wales site is a ‘reflection’ of visiting Ewloe Castle in the 1800s:  http://www.castlewales.com/ewloe1.html

There is no mention of Ewloe playing a role in either the war of 1277, which Llywelyn ap Gruffydd lost, or in 1282.